1. Field of the Invention
This invention relates to a process for producing polyolefins. More particularly it relates to a process for producing an odorless polyolefin by the use of a novel supported type solid catalyst. Polyolefins referred to herein mean homopolymers and copolymers of .alpha.-olefins having 3 or more carbon aooms, and also copolymers of .alpha.-oleiins having 3 or more carbon atoms with an .alpha.-olefin having two carbon atoms, the proportion of the former oomponent in the copolymers being 50% by weight or greater.
2. Description of the Prior Art
Heretofore as to the trend of improvement in the Ziegler-Natta type catalysts, it has been known that when a supported type solid catalyst component is combined with an organoaluminum compound component and an aromatic carboxylic acid ester component, the resulting polyolefin has an enhanced stereoregularity. For example, as disclosed in Japanese Patent Application Laid-Open Nos. Sho 57-74307/1982 and Sho 58-32604/1983, there is known a process wherein an aromatic carboxylic acid ester is added as a catalyst component to improve the stereoregularity of the resulting polyolefin. However, when polyolefins are produced according to gas phase polymerization wherein no solvent is used in principle, an aromatic carboxylic acid ester as a component of the catalyst is to be totally contained in the produced polyolefins. Further, it is well known that aromatic carboxylic acid esters give off a strong smell even when they are present in a slightest quantity. Thus, when polyolefins are produced according to gas phase polymerization using an aroamtic carboxylic acid ester as a catalyst component, the resulting polyolefins contain the aromatic carboxylic acid ester or a compound into which the ester has been converted during the polymerization process, and give off a strong smell during the storage of the polyolefins and during the granulation step of the polyolefins. This may raise a problem of environmental pollution in the case of polyolefin production on a commercial scale.
On the other hand, Japanese Patent Application Laid-Open No. Sho 58-83006/1983 discloses a process for producing polyolefins by the use of a catalyst formed by combining a supported type solid catalyst component with an organometal compound component and an organic silicon compound component having a Si--O--C or Si--N--O bond. In the case of this prior application, it is an indispensable requirement that the supported type solid catalyst component to be combined with the organic silicon componnd component contains a polybasic carboxylic acid ester and/or a polyvalent hydroxyl compound ester. However, it has not yet been known that even when a supported type solid catalyst containing an aromatic monocarboxyiic acid ester is combined with an ogganic silicon compound component having Si--O--C bond, the stereoregularity of the resulting polyolefins is improved. In addition, the organic silicon compound having Si--O--C bond gives off a weak smell and has a nature that it reacts relatively easily with the atmospheric moisture and is decomposed into an odorless compound. Thus, even when an organic silicon compound having Si--O--C bond is contained in a small quantity in polyolefins, such polyolefins are odorless.
The present inventors have made extensive research in order to solve the above problems of the environmental pollution and operational difficulty based on the strong smell, and as a result, have found that when a novel solid catalyst component containing an aromatic monocarboxylic acid ester is combined with an orgaoaluminum compound component and an organic silicon compound component having Si--O--C bond, the resulting catalyst has a high polymerization activity to such an extent that, when the catalyst is used for olefin polymerization, it is unnecessary to remove the catalyst residue contained in the resulting polymer, and the polymer afforded by this catalyst has a high stereoregularity, no smell and a good particulate form.
As apparent from the foregoing, the object of the present invention is to provide a process for producing polyolefins having a high stereoregularity, no smell and a good particulate form, without needing removal of catalyst residue contained in the resulting polyolefins.